As used herein, the terms "antimicrobial", "bactericidal", and "fungicidal" describes the killing of, as well as the inhibition of or control of the growth of bacteria and fungi.
Epoxy resins, as used herein, are thermosetting resins based on the reactivity of the epoxide group. One type is made from epichlorhydrin and bisphenol-A. Molecules of this type have glycidyl ether structures in the terminal positions, have many hydroxyl groups and cure readily with amines. Other suitable epoxy resins include glycidated novolacs, epoxylated novolacs, and cycloaliphatic epoxy resins. The reactive epoxies form a tight cross-linked polymer network, and are characterized by toughness, good adhesion, corrosion and chemical resistance, and also have good dielectric properties.
Bacteria, fungi and other microorganisms are always present in our environment. The species and numbers of microorganisms vary depending on the general environment, on the nutrients and moisture available for the growth of the microorganisms, and on humidity and temperature of the local environment. Nutrients for these microorganisms abound in the normal environment. Any protein matter such as dried skin, discarded foods, plants and animal droppings all are excellent nutrient media for many types of potentially harmful microorganisms. In addition certain bacteria are capable of remaining viable in a dormant state on floors or on objects for long periods of time until they are deposited in the proper media for growth. These potentially harmful microorganisms can be transported merely by walking on floors, brushing against walls or by handling objects.
The floors and walls found in buildings such as hospitals are particularly susceptible to contamination by bacteria and other harmful organisms. In fact, the floors and walls of hospitals are a major source of nosocomial (hospital-acquired) infections. Conventionally, these surfaces are periodically cleaned with cleansers to remove accumulated microorganisms. Between these cleanings, however, it is quite possible that the surfaces may accumulate a sufficient quantity or quality of bacteria or other microorganisms to constitute a major source of cross-infection or spread of disease.
Microorganisms contamination on walls and floors is also a major problem in industry. For example, the floors of breweries must often be repainted due to the constant yeast contamination from the fermentation process. The organisms apparently reside either on the surface of the floor under the paint or in the floor substrate (such as in concrete) under the paint and cause conventional floor coverings such as epoxy, to detach after a short period of time. The problem of microorganism contamination from walls and floors is particularly serious in industries which manufacture health related products such as drugs or biodiagnostic chemicals. Tremendous resources are expended in an attempt to reduce microorganism contamination in these industries.
Another major source of microbial contamination is from the handling of everyday objects. Bacteria and other microorganisms that are present in the environment will often be deposited on an object that is handled by several people. When one person puts the object down and another person picks it up, the microorganism can easily be transferred from the first person to the object and then to the second person. This is an especially harmful problem in hospitals where medical personnel routinely travel from one patient to another and can inadvertently transfer an especially serious microorganism to an object such as a medical chart, a pencil or any other object. A second medical personnel will then touch the object (called a fomite) and transfer the microorganism to their body. If the second medical personnel then examines or treats a second patient, the microorganism may be transferred to that patient and cause a serious secondary infection in the patient or even in the medical personnel.
A major problem encountered in the control of microorganisms is the extreme variability of response of the various microorganisms to conventional sanitizing agents. For example, bacteria, which are classified as prokaryotes, can be killed or inhibited by many different types of antibiotics. These same antibiotics that are highly effective against the prokaryotic organisms are usually highly ineffective against the eukaryotic microorganisms such as fungi and yeasts. Even within the family of Bacterioaceae, there are two broad categories of bacteria known as gram-positive and gram-negative bacteria. The classifications stem from the ability or non-ability of bacteria to absorb certain vital stains. The two groups of bacteria generally respond quite differently to the same microbiocidal agent. A particular agent that may be highly effective against one group, very likely may not be effective against the other group.
One conventional method of inhibiting the growth of both eukaryotes and prokaryotes and gram-negative and gram-positive bacteria is to combine two or more microbiocidal inhibitors; each designed to inhibit or kill a specific organism or class of organisms. However, various problems arise when introducing two or more additives into a material such as epoxy resin. The multiple additive system may alter the physical properties of the epoxy resin into which it is added. In addition, the multiple components must be tested to ensure their compatibility and continued microbiocidal effectiveness when combined with the material to be sanitized. The relative microbiocidal or microbiostatic strength of each of the components in the multiple system must be determined. It is not uncommon to produce an epoxy resin which may initially have effective inhibiting properties for both gram-positive and gram-negative organisms whereupon, with the passage of time, one or the other of the inhibiting additives will deteriorate and greatly lose its effectiveness while the other inhibiting additive remains effective. One additive may have an unexpected inhibitory effect on the other additive. In addition, the requirement of adding two or more additives can become prohibitively expensive.